| Summary: | An 8-week feeding trial was conducted to evaluate the effects of xylooligosaccharde (XOS) on growth, immunity and disease resistance of juvenile grass carp (Ctenopharyngodon idella). Fish (3.05 ± 0.01 g) were fed with diets containing XOS at levels of 0, 0.05 %, 0.1 %, 0.2 %, 0.4 % and 0.6 %. Results showed that the plasma triglyceride content was significantly lower in fish fed dietary 0.05 % and 0.1 % XOS compared to the control group (P < 0.05). Fish fed dietary 0.05 %, 0.1 % and 0.2 % XOS displayed significantly higher final body weight, weight gain and specific growth rate compared to the control group (P < 0.05). Fish fed 0.1 % XOS had significantly lower plasma malondialdehyde content and higher lysozyme activity than the control group (P < 0.05). XOS did not affect liver superoxide dismutase activity and glutathione content, but significantly reduced MDA content (0.4 % and 0.6 %) (P < 0.05). After Aeromonas hydrophila challenge, 0.1 % XOS significantly improved the survival rate of C. idella compared to that of the control diet (P < 0.05). Thus, the most suitable dietary supplementation level of XOS is 0.1 % for C. idella.
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